The heart of a computer is a magnetic hard disk drive (HDD) which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
Additionally, the read and write heads include a hard bias film, which constitutes a structure arranged on the end portion of a free layer, and applies a hard bias field (HBF) to the free layer. If the HBF is strong enough, the free layer is thereby formed as a single magnetic domain by the HBF, and run time noise is suppressed. However, when the HBF is weak, the free layer possesses varying magnetic domains, thereby generating undesirable run time noise, including Barkhausen noise.
The volume of information processing in the information age is increasing rapidly. In particular, HDDs have been desired to store more information in its limited area and volume. A technical approach to this desire is to increase the capacity by increasing the recording density of the HDD. To achieve higher recording density, further miniaturization of recording bits is effective, which in turn typically requires the design of smaller and smaller components. However, the further miniaturization of the various components presents its own set of challenges and obstacles.
Moreover, conventional attempts to increase recording densities have led to a size reduction of the read gap, which serves as a vertical magnetic shield interval, thereby inadvertently decreasing the HBF as well. Additionally, conventional attempts to increase recording densities have caused a reduction in the absorption of the HBF by the magnetic shield, also causing an undesirable decrease to the HBF. Thus it may be desirable to increase recording densities, while maintaining a HBF high enough to ensure a single magnetic domain free layer.